Take a photo of a barcode or cover
I read this book as a child and loved it very much. Every time I read it, I discover new things to love. The ideas in this book, and the book itself, spring to mind when I least expect it. I had forgotten the ambiguity in the ending and still have no concrete opinion on its meaning. Which I appreciate, as it allows me to come back to it again and again. And, of course, "back and back and back".